In construction of commercial offices, immediately visible ceilings are often comprised of lightweight fiber panels supported from a horizontal framework of aluminum struts and T- or L-cross section pieces, which also generally will include recessed lighting fixtures. The visible portion of the internal ceiling is actually supported from a horizontal structure above it, which horizontal structure has sufficient structural strength to prevent the suspended ceiling from falling into the room space below. Said horizontal structure may be formed of metal beams or plates, wood beams or sheets, concrete, or similar structural materials.
It is well known that installation of suspended ceilings is generally accomplished by way of first setting anchors into the horizontal structure by workers standing at floor level, which is often a distance of five or more feet from a worker's elevated arms. Because of the number of anchors required for installation of suspended ceilings from the horizontal structure, it is not efficient for workers to use a ladder to set said anchors. Instead, it is common practice for workers to use a special tool with an explosive charge device and anchoring shaft at the end of a pole to work from ground level to fix said anchors to the horizontal structure, as shown and described in U.S. Pat. No. 5,544,800, which incorporated by reference herein.
U.S. Pat. No. 4,979,715 discloses the simplest anchor and twisted hanger assembly, one which uses a screw as an anchor that must be directly screwed into a horizontal structure. U.S. Pat. No. 8,602,365 discloses a method of attaching a threaded positioner on a hanging threaded rod. U.S. Pat. No. 5,667,181 discloses an anchor with a nut with a single diameter, but which can be replaced with a nut of a different diameter. U.S. Pat. No. 3,266,202 discloses an anchor using a triangular flange but introducing an efficient means for forming a threaded section in the anchor, i.e., stamping lateral semi-circular sections in adjacent and opposite directions, within which concave portions are formed threads. U.S. Pat. No. 2,725,127 discloses an anchor that is capable of supporting a threaded hanging rod of a single diameter.
Some of the problems hanger assemblies of anchors and their threaded hanging rod have been their cost, multiple parts, and difficulty of installation. Such hanger assemblies have a minimum of three parts and may have five or more, depending on whether a separate fixing device or washer is employed. Since the installation is usually done on a scaffold or step ladder, loose parts can be a problem. Even if all of the parts as a set are packaged, the opening of the package and assembly of the parts can be a problem. If one of the parts drops or rolls away, the installer has to climb down to retrieve the part, if it can be found, or get another package. Multiple part fasteners always take more time to install, and are more costly, especially if packaged.
Structural and weight requirements of a specific area of a suspended ceiling are often not known beforehand. It is well known that later modifications to a planned installation of a suspended ceiling may require a change in diameter of threaded hanging rods than those installed in said anchors, requiring either installation of adjacent anchors capable of receiving greater diameter threaded hanging rods or manually changing nuts by tedious ladder supported work as in the '181 patent.
There is a need for an anchor for suspended ceilings which is inexpensive, lightweight, and can accommodate more than one diameter of threaded hanging rods.